The present invention relates generally to the field of doors, and more particularly to door structures having improved sound attenuation properties and extended fire ratings.
Doors with enhanced acoustical ratings are used to minimize noise in buildings such as condominiums, school classrooms, defense installations, theaters, etc. Typically, the sound ratings for these doors are relatively low, e.g., less than 32 Sound Transmission Class (STC) rating, due to the natural resonance frequency of materials and design used to construct doors. Various attempts have been made to improve the sound ratings of doors. For example, doors having a laminated surface and internal air space have been developed. However, the sound attenuation properties of such door structures are limited by the size of the air space.
Steel doors, which may display sound ratings greater than 45 STC, are commonly used for acoustical purposes. Steel doors are also more likely to carry fire ratings than combustible material doors. However, steel significantly increases the weight of the door.
Thus, the STC rating one can reasonably achieve in a normal 1.75″ thick door having a reasonable weight, e.g., less than about 200 lbs., and preferably less than about 175 lbs., is limited. Accordingly, there is a need for door structures having improved sound attenuation properties and extended fire ratings.